Silicone caulk / grout / mold under caulk


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Old 03-29-21, 09:00 AM
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Silicone caulk / grout / mold under caulk

5 years ago we had a bathroom done by someone else (I won't call him a pro... overall a bunch of appearance issues... so maybe functional errors also?). Since then, I've been in there. So I'm not sure who did the caulking but in some spots we have black mold under the caulk.

These pics are from under the step into the shower, looking from inside the shower outward.

Some questions:

1) Is using caulk in a shower acceptable? It would cover cracking of grout in corners (from settling / shifting?). But grout does allow water to wick under caulk to allow mold to grow?

2) If it's OK to use caulk in the shower, how do you keep water from wicking under the caulk / mold forming? Sealing grout would slow that down, but am I wrong to think that grout, even sealed will always? eventutally? allow water through it?

3) How would you remedy this mold? Remove the caulk? use a smaller bead (less caulk / less area for mold to get under it?). But you would still get mold under caulk under the grout / it's unavoidable?

THANKS!



 
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Old 03-29-21, 09:08 AM
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1. Yes, caulk is often used where two different planes meet like wall to floor because it's an area where grout frequently cracks.

2. Water will almost always find a way through. Grout is not waterproof so I think much of the water gets behind caulk by seeping through the grout.

3. Remove all the old caulk, clean and replace with new mildew resistant caulk.
 

Last edited by Pilot Dane; 03-30-21 at 09:16 AM.
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Old 03-30-21, 08:50 AM
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All floors have some movement. Caulk has some "give", Grout has none.
 
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Old 03-30-21, 12:20 PM
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This is perfect example why you should never use that old tech Silicon caulk in a shower. Can not tell you how many bathrooms I have had to do the exact same clean up.

Siliconized Latex caulk with Microban is new, modern, and works!
 
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Old 03-30-21, 01:08 PM
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Doesnt even look like silicone to me. Photo 1 and 2... Silicone doesn't crack like that.

And just a guess but I would suspect that the source of the mold is probably wood under the curb that is getting wet.
 
 

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